A scalable BSIM3v3 RF model for multi-finger NMOSFETs with ring substrate contact

Abstract

We propose a scalable RF subcircuit FET model using BSIM3v3 by adding one of BSIM4's Intrinsic Input Resistance (IIR) models (rgateMod=3) for S/sub 11/ scalability as well as a simple RC substrate network with well defined intrinsic FET's parasitic estimation including partitioned junction diodes for S/sub 22/ scalability. Using this simple model, we could achieve a reasonable scalability with variations of L, W, V/sub GS/, and V/sub DS/ for S/sub 11/ up to 25 GHz. We also suggest new S-parameter test structure for FETs with Ring Substrate Contact (RSC). This new layout scheme allows for improved S/sub 22/ scalability up to about 10 GHz; as well as reduces the punch through effect in DC I-V characteristic of large width NFETs. In addition, comparing to NFETs without RSC, we also report substantial R/sub sub/ lowering, FT and NF/sub min/ worsening, and C/sub sub/ influence on S/sub 22/ contours for NFETs with RSC in detail.